1. Field of the Invention
The present invention is directed to drilling fluid processing systems; to hydrocyclones used in such processing; to such hydrocyclones with a selectively adjustable inlet for drilling fluid; and to methods for using such systems and such hydrocyclones.
2. Description of the Related Art
In the drilling of a wellbore, a drill bit attached to the lower end of a drill string is rotated and lowered to form a hole in the earth. A drilling fluid is circulated through the hole, normally down the drill string to the bottom of the hole and upward through the annulus to the surface of the earth. The drilling fluid is referred to as drilling “mud”. The circulating drilling mud cools and lubricates the drilling bit and drill string, removes earth cuttings and solids from the hole, forms a filter cake on the hole wall, and/or controls formation pressure. Drilled solids can accumulate in the drilling mud and, if not removed, can adversely affect the hole and the drilling operations.
There are a variety of known drilling fluid processing systems, including, for example, but not limited to, those in U.S. Pat. Nos. 6,868,972; 6,669,027; 6,662,952; 6,352,159; 6,510,947; 5,861,362; 5,392,925; 5,229,018; 4,696,353; 4,459,207; 4,495,065; 4,446,022; 4,306,974; 4,319,991; and 4,116,288 (all said patents incorporated fully herein for all purposes).
Hydrocyclones are used in some known systems and methods to treat drilling muds to remove solids. Some typical hydrocyclones are separators with a separation chamber which, in some systems, is a generally cylindrical and conical separation chamber with an inlet, with an apex outlet located adjacent the apex of the cone, a vortex finder, and a vortex finder outlet located adjacent a base of the cone. Drilling mud is fed into the inlet and the inlet flow is converted into a flow with a tangential velocity along an inside wall of the separation chamber. The circular path of the flow results in centripetal acceleration which is applied to settling velocities of the suspended solids, driving larger and heavier particles outwardly toward the conical wall into an accelerating spiral along the wall to the apex outlet. These solids discharge at the apex of the cone. The liquid phase of the drilling mud, carrying smaller and lighter drilled solids, moves as a spiraling vortex to the vortex finder outlet.
U.S. Pat. Nos. 1,832,256; 2,870,990; 2,919,898; 2,941,783; 2,954,871; 3,016,962; 3,025,965; 3,057,476; 3,353,673; 3,358,833; 3,385,437; 3,766,997; 3,887,456; 3,893,914; 3,959,139; 3,964,557; 4,090,523; 4,134,828; 4,175,036; 4,226,708; 4,793,925; 5,108,608; 5,225,082; 5,240,115; 5,560,818; 5,858,237; 6,129,217; 6,533,946; 6,596,169; 6,855,261; 7,293,657; 7,438,142; and U.S. application Ser. No. 11/294,902 filed Dec. 6, 2005, Pub. No. 2008/0135300 published Jun. 12, 2008 disclose hydrocyclones and/or systems and methods which use hydrocyclones to treat drilling fluid—all said patents and said application incorporated fully herein for all purposes.